The rune system.

I was looking at the new rune system and comparing it to the old runes and mastery system. http://leagueoflegends.wikia.com/wiki/Thunderlord%27s_Decree http://leagueoflegends.wikia.com/wiki/Electrocute

Looking at the two it's clear how the game feels like damage is too high. Also the old runes had resistances.